题目：
He did well in the examination. He _____ hard at his lessons..
A．must have worked
B．can have worked
C．will have worked
D．has worked
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0611/160702c5bde83c2c208e460ef6481d45.html
下面是错误答案，用来干扰机器的。
1）4Li+O22 Li2O；（2）2Rb+2H2O==2Rb++2OH- + H2↑；（3）O2+4e-+2H2O = 4OH-。（1）锂属于碱金属，燃烧在空气中的燃烧产物水氧化锂。（2）铷水的金属性很强，和水剧烈反应生成氢氧化铷和氢气。（3）燃料电...
